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Cardiovascular > Physiology > Flashcards

Physiology Flashcards

1
Q

what is automaticity

A

the ability of the heart to beat in the absence of external stimuli

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2
Q

what is normal sinus rhythm

A

automaticity originating from the sino atrial node

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3
Q

where is the SA node located

A

within the right atrium near the entrance of the SVC

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4
Q

what causes the wave of depolarisation within the SA node

A

K+ efflux

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5
Q

what causes the wave of repolarisation within the SA node

A

activation of L-type calcium channels and influx of calcium

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6
Q

describe calcium induced calcium release

A

increasing the concentration of intracellular calcium causes more to be released from the SR

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7
Q

what is the spread of the conduction of the heart after the SA node

A

atrio-ventricular node - bundles of His - perkinje fibres

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8
Q

the inner wall of the ventricles conduction is supplied by

A

perkinje fibres

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9
Q

where is the AV node located

A

base of the RA

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10
Q

the AV node slows/speeds up conduction between atria and ventricles

A

slows down

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11
Q

why is the speed of conduction slowed down at the AV node

A

to allow the atria to complete systole before the ventricles begin to contract

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12
Q

the AVN is the only point of conductivity between atria and ventricles true/false

A

true

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13
Q

in ventricular muscle action potential what is the change in voltage between phase 0 and phase 1

A

-90mV to +20mV

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14
Q

what does phase 0 of ventricular action potential represent

A

rapid Na influx

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15
Q

what does phase 1 of ventricular action potential represent

A

closure of Na channels

K efflux

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16
Q

what does phase 2 of ventricular action potential represent

A

Ca influx through L-type channels

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17
Q

what is phase 2 also known as and why

A

plateau phase because membrane potential is very close to its peak for some time

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18
Q

what does phase 3 represent

A

closure of Ca channels

K efflux

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19
Q

what does phase 4 of ventricular action potential represent

A

resting membrane potential at -90mV

closure of K channels

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20
Q

sympathetic nervous system __ heart rate and conductivity

A

increases

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21
Q

sympathetic nerves act act on __ mediated by __

A

B1 adrenoceptors mediated by adrenaline/noradrenaline

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22
Q

parasympathetic nerves ___ heart rate and conductivity

A

decrease conductivity but no effect on nodal cells

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23
Q

parasympathetic innervation through CN__

A

X

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24
Q

vagal tone increases/decreases the slope on pacemaker potential

A

decreases

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25
Q

cardiac muscle is striated/non-striated

A

striated

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26
Q

what gives cardiac muscle its striated appearance

A

dark and light bands of myosin and actin

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27
Q

actin slides over myosin or myosin slides over actin?

A

actin slides over myosin

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28
Q

muscle fibres are arranged into what functional unit

A

sarcomeres

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29
Q

define stroke volume

A

volume of blood ejected by each ventricle per heartbeat

EDV - SSV

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30
Q

what does the frank-starling curve show

A

the more a ventricle is filled during diastole due to stretch of the myocytes, the greater the volume of ejected blood will be during followed contraction

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31
Q

heart failure has a negative inotropic effect - what does this mean

A

decreases contractility of the heart

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32
Q

define cardiac output

A

volume of blood ejected by each ventricle per minute

stroke volume x heart rate

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33
Q

what is the cardiac cycle describing

A

stages occurring from the beginning of one heart beat o the beginning of the next

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34
Q

what are the 5 events in the cardiac cycle

A 
passive filling 
atrial contraction 
isovolumetric ventricular contraction 
ventricular ejection 
isovolumetric ventricular relaxation
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35
Q

what occurs during passive filling

A

pressure between atria and ventricles almost zero - AV valves open allowing passive venous return into ventricles

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36
Q

what % of blood moves from atria to ventricles by passive filling

A

80%

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37
Q

what occurs during atrial contraction

A

remaining volume moves between atria and ventricles

occurs between P and QRS complex

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38
Q

what happens during isovolumetric ventricular contraction

A

AV valves shut and pressure within the ventricles rises

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39
Q

what happens during ventricular ejection

A

ventricular pressure > aortic/pulmonary pressure so AV valves open

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40
Q

what happens during ventricular relaxation

A

blood moves through AV valves causing closure

ventricular pressure < atrial pressure so meaning AV valves open and new cycle starts

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41
Q

what is blood pressure

A

the outwards hydrostatic pressure exerted by the blood on vessel walls

42
Q

systolic BP is during

A

contraction

43
Q

diastolic BP is during

A

relaxation

44
Q

the sounds heard when auscultating blood pressure are known as

A

Korotkoff sounds

45
Q

1 korotkoff sound represents

A

systolic blood pressure

46
Q

5/final sound represents

A

diastolic pressure - silence

47
Q

what is the formula for calculating mean arterial blood pressure

A

(2xdiastolic + systolic)/3

1/3(systolic-diastolic + diastolic)

48
Q

what is the normal range for mean arterial blood pressure

A

70-105mmHg

49
Q

what are the main resistance vessels in the body

A

arterioles

50
Q

what controls the short term regulation of blood pressure

A

baroreceptors

51
Q

where are the baroreceptors located

A

aortic and carotid arteries

52
Q

which cranial nerve supplies the carotid baroreceptor

A

glosspharyngeal nerve (CN IX)

53
Q

which cranial nerve supplies the aortic baroreceptor

A

vagus nerve (CN X)

54
Q

how do the baroreceptors change MAP

A

pressure sensors detect change in MAP - send signal to medulla - triggers effectors in heart to alter HR, SV, SVR

55
Q

if blood pressure is high - baroreceptors causes HR, SV, SVR to increase/decrease

A

all decrease

56
Q

what is postural hypotension

A

failure of the baroreceptors to respond immediately to a change in gravitational shift

57
Q

postural hypotension is defined as

A

drop in systolic bp by 20mmHg or drop in systolic bp by 10mmHg plus dizziness, lightheadedness or blurred vision

58
Q

what controls the long term regulation of blood pressure

A

regulation of extracellular fluid (composed of plasma volume and interstitial fluid) - through excess/deficit water and Na

59
Q

what 3 hormonal systems regulate bp long term

A

RAAS
natriuretic peptides
ADH

60
Q

what substance is released from the kidneys when bp is low

A

renin

61
Q

renin goes on to activate __ regulated by which enzymes

A

angiotensin I - angiotensin II - aldosterone

angiotensin converting enzyme responsible for change

62
Q

what effect does aldosterone have once released from adrenal cortex

A

causes sodium and water retention causing blood pressure to rise

63
Q

natriuretic peptides provide the same/different response as RAAS

A

different - acts counter regulatory mechanism causing excretion of sodium and water

64
Q

where is ANP released from

A

atria due to atrial distension

65
Q

where is BNP released from

A

the brain in response to stretch in the ventricles

66
Q

what is ADH

A

peptide hormone derived from pre-cursor in the hypothalamus

secretion stimulated by increase in extracellular fluid volume

67
Q

what is the effect of ADH release

A

increases water reabsorption in kidney tubules and vasoconstriction of blood vessels

68
Q

resistance to blood flow is directly proportional to

A

blood viscosity and length of vessel

69
Q

resistance to blood flow is inversely proportional to

A

radius of the blood vessel to the power of 4

70
Q

what is vasomotor tone

A

due to sympathetic stimulation blood vessels are partially constricted at rest

71
Q

do parasympathetic nerves innervate arterial smooth muscle

A

no - except in the penis and clitoris

72
Q

name some humoral agents that cause smooth muscle dilatation

A

histamine
bradykinin
nitric oxide

73
Q

name some humoral agents that cause smooth muscle constriction

A

thromboxane

leukotrienes

74
Q

define the term shock

A

abnormality of circulatory system resulting in decreased tissue perfusion

75
Q

what is hypovolaemic shock

A

shock due to loss of blood volume - can be due to trauma, vomiting, diarrhoea

76
Q

what causes cardiogenic shock

A

sustained hypotension due to reduced cardiac contractility. results in hypoperfusion of vessels

77
Q

pneumothorax is an example of which type of shock

A

obstructive - SVC becomes obstructed and inter-thoracic pressure increases

78
Q

what causes vasoactive shock

A

release of vasocative mediators such as NO causing excessive vasodilation

79
Q

what causes neuorgenic shock

A

loss of sympathetic tone causing excessive vasodilation

80
Q

compensatory mechanisms can maintain BP until how much blood is lost

A

30% of total volume

81
Q

what is the bodys response to shock

A

increase sympathetic tone and vasoconstriction

82
Q

what are some adaptations of coronary circulation to allow high oxygen demand

A

high number of capillaries
high basal blood flow (at rest)
high oxygen extraction rates

83
Q

if the heart wants to increase oxygen to area what is done

A

must increase coronary blood flow because oxygen rate in blood is already so high

84
Q

if coronary PO2 is low blood vessels vasodilate/vasoconstrict and why

A

vasodilate and oxygenation to that are needs to be improved

85
Q

where specifically in the brain is very sensitive to hypoxia

A

grey matter

86
Q

which arteries supply the brain

A

internal carotids

vertebral arteries

87
Q

which arteries make up the circle of Willis

A

basilar and vertebral arteries

88
Q

what range must cerebral blood pressure be within for correct perfusion and autoregulation

A

60-100mmHg

89
Q

if MAP rises in cerebral circulation blood vessels dilate/constrict

A

dilate to decrease blood pressure

90
Q

what blood pressure causes fainting and confusion in cerebral circulation

A

50mmHg or less

91
Q

decrease in PCO2 causes vessels to

A

constrict

92
Q

what causes a rise in intercranial pressure

A

trauma etc

93
Q

what does an increase in intercranial pressure do to cerebral perfusion pressure and cerebral blood flow

A

reduces both

94
Q

which substances can and cannot penetrate the blood brain barrier

A

O2 CO2 and glucose can all penetrate BBB

ions and proteins cannot

95
Q

why can specific substances not pass the BBB

A

protects the neurones

96
Q

what is the pressure within the pulmonary circulation

A

5-8mmHg

97
Q

what mechanism prevents oedema in pulmonary circulation

A

absorptive forces are greater than filtration forces

98
Q

hypoxia causes vaosdilatation/vasoconstriction in pulmonary arteries

A

vasoconstriction - diverts blood from poorly ventilated area of the lung

99
Q

during exercise what happens to blood floow of skeletal muscle

A

increases

100
Q

in skeletal muscle what overrides sympathetic vasoconstrictor activity

A

metabolic hyperaemia

Cardiovascular (8 decks)

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